Rectifier device



Feb. 13, 1940. w KALBsKoPF 2,189,905

RECTIFIER DEVICE Filed June 17, 1938 www? Patented Feb. 13, 1940 massesBECTIFIEB DEVICE walter Kalbskopf, Nuremberg, Germany, signor toBuddeutsche Apparatefabrik, Nuremberg,

Germany, a company Application June 1'1,

In Germany 4Ciaims.

'Ihe present invention relates to electrical networks includingrectiiler devices, and more particularly to rectiiier circuitarrangements adapted to change an alternating current of one wave 5fshape to an alternating current of the same frequency but oi differentwave shape.

It is frequently desirable to feedglow lamps such as iilament lamps witha low'frequency alternating current, e. g., of 16% cycles per second, asusually employed in electric railway operation. As a matter of fact, analternating current of customary wave shape e. g. sinusoidal, generatedwith a periodicity of only 16% cycles per second is not well adapted forsupplying such 1I lamps so that the light therefrom is free ofilickering since the heat inertia of the lamp lament generally will beinsumcient for securing a steady light. This heat inertia may beincreased by simultaneously increasing the cross sectional n area of theiilament and decreasing the supply voltage. The ickering tendency of theglow lamp filament diminishes in proportion to the decrease of thesupply voltage ata given power. If the voltage for any reasons cannot bekept g at a sumciently low value, means must be provided in order toobtain a more uniform amplitude characteristic of the lamp current withrespect to time so as to prevent ickering of the emitted light.

Such correction of the alternating current may be performed byrectiiying and smoothing the total alternating current energy. Theresulting rectied and smoothed current is then applied to the vglowlamps. However, the technical 'solution of this problem makes itnecessary to dimension the rectiers so as to withstand the totalamperase and total voltage of the load current, a requirement whichintroduces considerable expenditure with respect to rectifying means oand which involves inevitable power losses.

It is true that with respect to a plural-phase alternating current therequirements of the smoothing means n for securing a nonickering lamplight are less than in the case of single phase currentoperation.However the total expenditure is considerable also in` plural phasesystems on account of the additional switching equipment for obtainingthe plural phase displacement.

The above conditions also apply substantially to other load devices suchas high power switching means or similar apparatus which-must bearranged so as to prevent vibrations of the armature of such apparatus.Heretofore this has been sa achieved by electrically or mechanicallydamp-- 1938, Serial No. 214;,22'1

June 23, 1937 ing the apparatus itself or by the agency of alternatingcurrent phase shifting means.

'I'he present invention provides the possibility of obtaining a steadylight from glow lamps fed by an alternating current of low periodicity,or I of operating relays with an alternating current of normal frequencywithout the disagreeable hum. These features are obtained according tothe invention by substantially less expensive equipment than heretofore.vl0

v The invention is founded on the idea that a non-flickering operationdoes not require rectication and subsequent smoothing of the totalalternating current power so as to energize the load device with aunidirectional current; on the contrary, by changing the alternatingcurrent wave shape so as to aproach a rectangular shape the desirednon-nickering results are obtained, sincethe current alternation fromits positive to its negative maximum amplitude would so rapidly takeplace that a glow lamp illament energized thereby would find no time forcooling. An approximate rectangular shape of the alternating current-wave shape would thus provide al suitable measure for avoidingili'ckering of glow lamps. 'I'he same applies to high power switchingrelays and the like operated with an alternating current of the abovementioned form.

The corresponding conversion of the alternating current wave shape intoan approximately vrectangular shape is accomplished according to thepresent invention by the provision of a rectifier bridge in one sideA ofthe load circuit supply line, said bridge having a choke coil connectedto the direct current diagonal thereof.

The invention will be more readily understood from the followingdescription taken in conjunction with the accompanying drawing, inwhich.

Fig. 1 is a diagram representing one embodiment of the invention, Fig. 2diagrammatically illustrates a modification over the arrangement shownin Fig. 1, Fig. 3 is a diagram showing still a further modificationaccording to the invention, while Fig. 4 shows the change of thealternating current wave shape which is obtained according to theinvention.

The rectiiier valves R intended for insertion in one side of the loadcircuit are interconnected in a full wave rectifier bridge fashion,similar to the so-called Graetz circuit as shown in Fig. 1, or inpush-pull as shown in Fig. 2. 'lhese valves must be dimensioned so as towithstand the total current ilowing in the load circuit, while theirdimensioning with respect to the voltage merely necessitates anaccommodation to the effective voltage of the harmonics of the rectlnedcurrent flowing through the choke coil S .so that the rectiiier` itselfmay be kept relatively compact.-

The circuit arrangement as illustrated in Fig. 2 involves the advantagethat at the same current intensity merely half as many rectiiier valvesR are required as compared with the arrangement shown in Fig. 1, but thechoke coil S must be provided with a center tapping point.

Fig. 4 shows the change with respect to the form of the alternatingcurrent wave shape resulting from interposing the rectifier valve andthe smoothing choke coil in the load circuit. The thin continuous curveI represents the wave shape of the alternating supply voltage. If theload is non-inductive, the current will be in phase with this curve. Thedash-dotted line II illustrates the current through the choke coil atcomplete rectiiication andsuiilcient smoothing.

In the arrangement according to the invention, a direct current ilowtakes place in the choke coil S only, and such choke coil will fullyexert its smoothing action upon this direct current, while thealternating current character of the current still prevails externallywith respect to the combined rectiiier and choke coil assembly, that'is,in the load circuit. However, the individual half-'waves of thealternating current are so attened and simulated to rectangularity bythe agency of the smoothing action of the choke coil S that thealternation from the positive to the negative half-wave, and vice versa,is effected 'with an utmost rapidity as indicated by the full curve DI.

A still further perfection with respect to the smoothing and hence ofthe rectangular shape of the alternating current characteristic asillustrated by the curve III of Fig. 4 may be achieved byshunting acondenser C across the choke coil S as shown in Figs. 1 and 2, said twoelements constituting an oscillatory circuit tuned to the frequency ofthe alternatingcurrent. Since the condenser of this oscillatory circuitwould have to be of considerable size at higher current intensities, anoscillatory circuit comprising a condenser C and an inductance L may beinductive- 1y coupled to the choke coil S as shown in Fig. 3 bysimultaneously stepping down the voltage so as to permit application ofa condenser of smaller capacity.

The rectiiler circuit arrangement according to the present invention forobtaining non-flickering operation of electric glow lamps supplied by alow frequency current, the characteristic of which is subjected to asuitable correction involves essential features over the knownarrangements of this kind since the same results are obtained at aminimized expenditure of rectifying means. 5

The arrangement heretofore disclosed and particularly as described andas shown in the drawing is applicable in al1 cases where an altematingcurrent is desired, the characteristic of which presents a very steepand sudden alternation from l0 the positive to the negative maximumamplitude, and vice versa. y

What is claimed is:

l. In combination, a source of alternating current having a. wave shapewith a gradual slope 16 from positive maximum to negative maximum,

a load device to be energized from said source said device having suchlittle inertia that it responds substantially in proportion to theinstantaneous value of the applied waves, and means to conn vert thealternating current into an alternating current of the same frequencybut with an abrupt slope between positive maximum and negative maximum,the last-mentioned means including a plurality of rectiiier unitsarranged I in the*I form of a bridge for full-wave rectiiication andconnected only in one side of the alternating current supply line and achoke coil connected in one diagonal of said rectifier bridge.

2. In combination, a source of alternating cur- .o

rent having a substantially sinusoidal wave shape,

ea load device to be energized from ,said source said device having solittle inertia that it responds substantially proportionately to theinstantaneous value of the applied alternating current, and means toconvert the alternating current from said source into an alternatingcurrent of the same frequency but with a substantially rectangular waveshape, the last-mentioned means including a plurality of rectiiler. ounits oi the dry rectifier type interconnected in push-pull fashion andconnected in only one side of the alternating current supply line, and achoke coil shunted across said rectiiiers.`

3. The combination according to claim 1 in 5 which a condenser isshunted across said choke coil to form an oscillatory circuit tuned tothe frequency of the alternating current supply.

4. The combination according to claim 1 in which an oscillatory circuitcomprising` an in- 50 ductance and a condenser tuned to the frequency ofsaid alternating current supply is inductively coupled to said chokecoll.

WALTER KALBSKOPF.

